backend barebone done, big chunk of work done

server/internal/store/contacts.go

@@ -0,0 +1,69 @@
+package store
+
+import (
+	"context"
+	"errors"
+
+	"github.com/jackc/pgconn"
+	"github.com/jackc/pgerrcode"
+)
+
+// AddContact creates a contact relation or returns ErrDuplicate if it exists.
+func (s *Store) AddContact(ctx context.Context, ownerID, contactID int64) error {
+	_, err := s.pool.Exec(ctx, `
+       INSERT INTO contacts(owner_id, contact_id)
+       VALUES($1, $2)
+   `, ownerID, contactID)
+	if err != nil {
+		var pgErr *pgconn.PgError
+		if errors.As(err, &pgErr) && pgErr.Code == pgerrcode.UniqueViolation {
+			return ErrDuplicate
+		}
+	}
+	return err
+}
+
+// RemoveContact deletes a contact relation; no error if not present.
+func (s *Store) RemoveContact(ctx context.Context, ownerID, contactID int64) error {
+	_, err := s.pool.Exec(ctx, `
+       DELETE FROM contacts WHERE owner_id=$1 AND contact_id=$2
+   `, ownerID, contactID)
+	return err
+}
+
+// ListContacts returns all contacts for an owner ordered by created_at descending.
+func (s *Store) ListContacts(ctx context.Context, ownerID int64) ([]Contact, error) {
+	rows, err := s.pool.Query(ctx, `
+       SELECT owner_id, contact_id, created_at
+       FROM contacts WHERE owner_id=$1
+       ORDER BY created_at DESC
+   `, ownerID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var list []Contact
+	for rows.Next() {
+		var c Contact
+		if err := rows.Scan(&c.OwnerID, &c.ContactID, &c.CreatedAt); err != nil {
+			return nil, err
+		}
+		list = append(list, c)
+	}
+	return list, nil
+}
+
+// IsContact reports whether a contact relation exists.
+func (s *Store) IsContact(ctx context.Context, ownerID, contactID int64) (bool, error) {
+	var exists bool
+	err := s.pool.QueryRow(ctx, `
+       SELECT EXISTS(
+           SELECT 1 FROM contacts WHERE owner_id=$1 AND contact_id=$2
+       )
+   `, ownerID, contactID).Scan(&exists)
+	if err != nil {
+		return false, err
+	}
+	return exists, nil
+}